Genetic analysis of a case of mild epilepsy due to variant of SCN9A gene

Abstract

To explore the genetic etiology of a patient with epilepsy and provide genetic counseling. A patient who had visited the Center for Reproductive Medicine of Shandong University on November 11, 2020 was selected as the study subject, and her clinic information was collected. Candidate variant was identified through whole exome sequencing (WES), and Sanger sequencing was used for validation. Possible transcriptional changes caused by the variant was detected by reverse transcription-PCR and Sanger sequencing. The patient was a 35-year-old female with no fever at the onset, loss of consciousness and abnormal firing in the temporal lobe, manifesting predominantly as convulsions and fainting. WES revealed that she had harbored a heterozygous c.2841+5G>A variant of the SCN9A gene, which was verified by Sanger sequencing. cDNA sequencing confirmed that 154 bases were inserted between exons 16 and 17 of the SCN9A gene, which probably produced a truncated protein and affected the normal function of the SCN9A protein. Based on the guidelines from the American College of Medical Genetics and Genomics, the c.2841+5G>A variant was classified as likely pathogenic (PVS1_Strong+PM2_Supporting). The c.2841+5G>A variant of the SCN9A gene probably underlay the epilepsy in this patient. Above finding has enriched the variant spectrum of the SCN9A gene and provided a basis for the prenatal diagnosis and preimplantation genetic testing for this patient.